This invention relates generally to human/computer interface devices, and more particularly to computer input devices such as mice, trackballs, etc.
Virtual reality computer systems provide users with the illusion that they are part of a xe2x80x9cvirtualxe2x80x9d environment. A virtual reality system will typically include a personal computer or workstation, specialized virtual reality software, and virtual reality I/O devices such as head mounted displays, pointer gloves, 3D pointers, etc.
For example, a virtual reality computer system can allow a doctor-trainee or other human operator or user to xe2x80x9cmanipulatexe2x80x9d a scalpel or probe within a computer-simulated xe2x80x9cbodyxe2x80x9d, and thereby perform medical procedures on a virtual patient. In this instance, the I/O device is typically a 3D pointer, stylus, or the like. As the xe2x80x9cscalpelxe2x80x9d or xe2x80x9cprobexe2x80x9d moves within the body image displayed on the screen of the computer system, results of such movement are updated and displayed so that the operator can gain the experience of such a procedure without practicing on an actual human being or a cadaver.
For virtual reality systems to provide a realistic (and therefore effective) experience for the user, sensory feedback and manual interaction should be as natural as possible. As virtual reality systems become more powerful and as the number of potential applications increases, there is a growing need for specific human/computer interface devices which allow users to interface with computer simulations with tools that realistically emulate the activities being represented within the virtual simulation. Such procedures as laparoscopic surgery, catheter insertion, and epidural analgesia should be realistically simulated with suitable human/computer interface devices if the doctor is to be properly trained.
While the state of the art in virtual simulation and medical imaging provides a rich and realistic visual feedback, there is a great need for new human/computer interface tools which allow users to perform natural manual interactions with the computer simulation. For medical simulation, there is a strong need to provide doctors with a realistic mechanism for performing the manual activities associated with medical procedures while allowing a computer to accurately keep track of their actions.
There are number of devices that are commercially available for interfacing a human with a computer for virtual reality simulations. There are, for example, such 2-dimensional input devices such as mice, trackballs, and digitizing tablets. However, 2-dimensional input devices tend to be awkward and inadequate to the task of interfacing with 3-dimensional virtual reality simulations. In contrast, a 3-dimensional human/computer interface tool sold under the trademark Immersion PROBE(trademark) is marketed by Immersion Human Interface Corporation of Palo Alto, Calif., and allows manual control in 3-dimensional virtual reality computer environments. A pen-like stylus allows for dexterous 3-dimensional manipulation, and the position and orientation of the stylus is communicated to a host computer. The Immersion PROBE has six degrees of freedom which convey spatial coordinates (x, y, z) and orientation (role, pitch, yaw) of the stylus to the host computer.
While the Immersion PROBE is an excellent 3-dimensional interface tool, it may be inappropriate for certain virtual reality simulation applications. For example, in some of the aforementioned medical simulations three or four degrees of freedom of a 3-dimensional human/computer interface tool is sufficient and, often, more desirable than five or six degrees of freedom because it more accurately mimics the real-life constraints of the actual medical procedure. Therefore, a less complex, more compact, lighter weight, lower inertia and less expensive alternative to six degree of freedom human/computer interface tool is desirable for certain applications.
The present invention provides a 3-dimensional human/computer interface tool which is particularly well adapted to virtual reality simulation systems that require fewer degrees of freedom, e.g. two, three, or four degrees of freedom. The present invention therefore tends to be less complex, more compact, lighter weight, less expensive, more reliable and have less inertia than 3-dimensional human/computer interface tools of the prior art having more degrees of freedom.
The present invention is directed to a method and apparatus for providing an interface between a human and a computer. The human end of the interface is preferably a substantially cylindrical object such as a shaft of a surgeon""s tool, a catheter, a wire, etc. Alternatively, it can comprise a pool cue, a screw driver shaft, or any other elongated object that is manipulated in 3-dimensional space by a human operator. In certain embodiments of the present invention, the computer develops signals to provide force feedback to the object. For example, a twisting or resisting force can be imparted on the object to provide haptic or force feedback of a medical procedure being performed in a virtual reality simulation.
An apparatus for interfacing with a electrical system includes a support, a gimbal mechanism coupled to the support, and preferably three electromechanical transducers, although certain embodiments (e.g. for use with catheters) may require only two electromechanical transducers. The gimbal mechanism has a base portion which is rotatably coupled to the support to provide a first degree of freedom, and an object receiving portion rotatably coupled to the base portion to provide a second degree of freedom. A first electromechanical transducer is coupled between the support and the base portion, a second electromechanical transducer is coupled between the base portion and the object receiving portion, and a third electromechanical transducer is coupled between the object receiving portion and an intermediate portion of an elongated object that is at least partially disposed within the object receiving portion. The third electromechanical transducer is associated with a third degree of freedom. Therefore, each of the three transducers are associated with a degree of freedom of movement of the object when it is engaged with the object receiving portion of the gimbal mechanism.
More specifically, an apparatus for interfacing an operator manipulable shaft with a computer includes a support, a gimbal mechanism, and four sensors.
The gimbal mechanism preferably includes a U shaped base portion having a base and a pair of substantially parallel legs extending therefrom, where the base of the U shaped base portion is rotatably coupled to the support, and a shaft receiving portion pivotally coupled between the legs of the base portion. The shaft receiving portion includes a translation interface and a rotation interface that engage the shaft when it is engaged with an aperture of the shaft receiving portion. The base portion rotates around a first axis and the shaft receiving portion rotates around a second axis substantially perpendicular to the first axis, such that an axis of the shaft defines a radius in a spherical coordinate system having an origin at an intersection of the first axis and the second axis. A first sensor is coupled between the support and the U shaped base portion to provide a first output signal, a second sensor is coupled between the U shaped base portion and the shaft receiving portion to produce a second output signal, a third sensor is coupled to the translation interface to produce a third output signal, and a fourth sensor is coupled between the rotation interface and the object to produce a fourth output signal. The output signals are preferably coupled to an input of a computer by an electronic interface.
In an alternative embodiment of the present invention a first actuator is coupled between the support and the U shaped base portion to produce a movement therebetween in response to a first input electrical signal, a second actuator is coupled between the U shaped base portion and the shaft receiving portion to produce a movement therebetween in response to a second input electrical signal, a third actuator is coupled to the translation interface to produce a mechanical movement of the elongated cylindrical object relative to the shaft receiving portion in response to a third input electrical signal, and a fourth actuator is coupled to the rotation interface to produce a mechanical movement of the elongated cylindrical object relative to the shaft receiving portion in response to a fourth input electrical signal.
A method for providing a human/computer interface includes the steps of: (a) defining an origin in a 3-dimensional space; (b) physically constraining a shaft that can be grasped by an operator such that a portion of the object always intersects the origin and such that the portion of the object extending past the origin defines a radius in a spherical coordinate system; (c) transducing a first electrical signal related to a first angular coordinate of the radius in the spherical coordinate system with a first transducer; (d) transducing a second electrical signal related to a second angular coordinate of the radius in the spherical coordinate system with a second transducer; (e) transducing a third electrical signal related to the length of the radius with a third transducer; and (f) electrically coupling the transducers to a computer system to provide a human/computer interface. The method can further include the step of transducing a fourth electrical signal related to a rotation of the shaft around an axis with a fourth transducer. The transducers are either sensors, actuators, or bidirectional transducers which can serve as either input or sensors.
It will therefore be appreciated that a human/computer interface of the present invention includes a support, a gimbal mechanism coupled to the support, and an elongated shaft engaged with the gimbal mechanism and having a grip area that can be grasped by a hand of an operator. The gimbal mechanism has a base portion rotatably coupled to the support, and a shaft receiving portion rotatably coupled to the base. A first sensor is coupled between the support and the base portion, a second sensor is coupled between the base portion and the shaft receiving portion, and a third sensor is coupled between the shaft receiving portion and an intermediate portion of the shaft. The three sensors are coupled to an input of a computer to provide the human/computer interface. Preferably, the interface further includes a fourth sensor coupled between the shaft receiving portion and an intermediate portion of the shaft, where the third sensor is a translation sensor and the fourth sensor is a rotation sensor.
The advantage of the present invention is that a 3-dimensional human/computer interface tool is provided which has the three or four degrees of freedom available that are desirable for many virtual reality simulation applications. The mechanism of the present invention is relatively straight-forward allowing for low cost production and high reliability. Furthermore, since the human/computer interface tool of the present invention is constrained from movement along at certain degrees of freedom, it can more accurately simulate the use of tools and other elongated mechanical objects which are similarly constrained. Importantly, the present interface is of low inertia since the primary mass of the interface is located at the pivot point. This, along with the light weight of the interface, makes the interface less fatiguing to use.
In another embodiment of the present invention a human/computer interface tool is provided which is provided with only two degrees of freedom. This is particularly advantageous when the shaft is flexible, such as with very thin shafts, wires, catheters, and the like. With, for example, catheters, it is only necessary to provide two degrees of freedom (i.e. in-and-out, and rotation) and, therefore, sensors and/or actuators for the other degrees of freedom do not need to be provided.